Imaging devices of this type are generally known in the form of x-ray machines. X-ray machines for digital X-ray imaging are currently being developed. The new-style x-ray machines for digital x-ray imaging use so-called flat-panel detectors (among other things) that can be classified as flat-panel detectors with direct conversion and flat-panel detectors with indirect conversion.
Flat-panel detectors with indirect conversion have a scintillator extended over the surface, which covers a read-out matrix made from amorphous silicon. Various materials may be used for the scintillator. Materials normally used are manufactured on the basis of CsI or Gd2O2S. The read-out matrix comprises a plurality of photodiodes which convert the light generated in the scintillator from incident x-rays, into electrical charges. These electrical charges are stored in the capacitors allocated to each of the individual photodiodes, and, after the recording process is complete, are read out by active switching elements and converted into digital data with the help of analog-digital converters.
In flat-panel detectors with direct conversion, the incident x-rays are converted into electrical charges in a photoconductive layer, which is typically made from amorphous selenium. The electrical charges are stored in electrodes adjoining the photoconductive layer, and then read out from the electrodes with the help of active switching elements.